Sleeve for optical connector ferrules and method for production thereof

ABSTRACT

Disclosed are a sleeve for abutting, aligning, and retaining opposed optical connector ferrules and methods for the production thereof. The sleeve has a tubular body provided at three points on the inner wall surface thereof with ridges of an arcuate cross section extending from one to the other end of the tubular body in the longitudinal direction thereof and a slit formed therein in the longitudinal direction thereof. The sleeve is formed of an amorphous alloy possessing at least a glass transition region, preferably a glass transition region of not less than 30 K in temperature width. Preferably the sleeve is formed of an amorphous alloy having a composition represented by the following general formula and containing an amorphous phase in a volumetric ratio of at least 50%:  
     X a M b Al c   
     wherein X represents either or both of two elements, Zr and Hf, M represents at least one element selected from the group consisting of Mn, Fe, Co, Ni, and Cu, and a, b, and c represent such atomic percentages as respectively satisfy 25≦a≦85, 5≦b≦70, and 0&lt;c≦35. Such a sleeve can be manufactured with high mass-producibility by a metal mold casting method or molding method.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] This invention relates to a sleeve for abutting, aligning, andretaining opposed ferrules for use in an optical connector to be usedfor connecting optical fibers and a method for the production thereof.

[0003] 2. Description of the Prior Art

[0004] Generally, the connecting part in an optical connector iscomposed of ferrules having connected thereto a sheathed optical fibercompleted by coating the basic thread of an optical fiber with a sheathand a sleeve shaped like a hollow cylinder and adapted to admit opposedferrules in an aligned state. Particularly unlike the electricconnector, the optical connector is required to ensure exact accordbetween the relative positions of two optical fibers to be connected.It, therefore, becomes necessary to fix an optical fiber in coincidencewith the center of a ferrule having the outside diameter thereof and theinside diameter of the part thereof for allowing insertion of the basicthread of an optical fiber finished in respectively specified sizes andthen insert a pair of such ferrules into a sleeve through the oppositeends thereof until mutual abutment, and center the axes of the opticalfibers. As means for effecting this centering, the methods of theso-called adjusting type which rely on adjusting mechanisms to carry outfine adjustment and the methods of the no-adjusting type which are aimedat heightening the dimensional accuracy of ferrules and sleeves areavailable. Recently, the methods of the no-adjusting type have beenpredominating.

[0005] Heretofore, most of the ferrules which have been in popular useare those made of such ceramic substances as zirconia. By the sametoken, the sleeves which are made of such ceramic substances as zirconiahave been in popular use.

[0006] Published Japanese Patent Application, KOKAI (Early Publication)No. (hereinafter referred to briefly as “JP-A-”) 6-27,348, for example,discloses a ceramic sleeve which is formed by providing a tubular bodywith ridges raised from at least three points on the inner wall surfaceof the tubular body and extended from one to the other end of the lengthof the tubular body. The ridge has an upper face formed in a concavecircular arc included in a circle centering about the axis of thetubular body, namely a concave arcuate cross section facing the axis ofthe tubular body. The ridges and the inner wall surface of the tubularbody are interconnected with gentle curves. The patent literaturementioned above further discloses a method for the production of thesleeve. This method comprises a step of manufacturing such a ceramic rawmaterial as zirconia or alumina into a tubular body of such a geometricshape as described above, a step of calcining the resultant tubularbody, and a step of polishing the upper faces of the ridges on the innerwall surface of the calcined tubular body. When the sleeve is a splittype, the method further comprises a step of inserting a slit in thetubular body fresh from the polishing step throughout the entire lengththereof in the longitudinal direction.

[0007] The ceramic sleeve constructed as described above is generallyproduced by subjecting the raw material first to primary forming in acylindrical shape as by powder extrusion or injection molding and thento degreasing and sintering treatments and machining works for grindingthe outer surface of the tubular body and abrading the inner wallsurface of the tubular body. The process of production, therefore,includes many steps and incurs an enormous cost inevitably. Further,since the raw material is brittle and rigid, the product brings aboutsuch problems as shedding chips and leaving the finish of surfacepolishing at the mercy of the grain size of crystals. Since the ceramicsleeve is rigid and deficient in elasticity, the ridges raised from theinner wall surface of the sleeve tend to inflict scratches on the outerfaces of the ferrules and the sleeve and the ferrules, on repeatingtheir mutual attachment and detachment, tend to backlash possibly to theextent of inducing a deviation from the axial alignment of the opticalfibers. The ceramic substance, therefore, is not perfectly fit as amaterial for the sleeve in the optical connector which is prone tofrequent attachment and detachment of the ferrules.

[0008] Further, since the ceramic sleeve inevitably contracts when it issintered subsequently to the primary formation, it must be ground toprescribe dimensions by all means. When the ridges are formed asextended in the longitudinal direction on the inner wall surface of thetubular body, therefore, the upper faces of the ridges are ground in aconcave arcuate shape along the axis of the tubular body as disclosed inJP-A-6-27,348 mentioned above. When these ridges are formed at threepoints on the inner wall surface of the tubular body, it is not theconcave arcuate faces of the ridges but the opposite lateral edges ofthese faces in the longitudinal direction that are actually exposed tocontact with the outer peripheral surfaces of the ferrules which havebeen inserted into the sleeve. When the component ridges of the sleeveare exactly in agreement in size, therefore, the sleeve is fated to fixthe ferrules in position in a state such that the opposite lateral edges(located at a total of six points) are held in contact with the outersurfaces of the ferrules. When the ridges involve a dimensional error,even if slightly, the contact occurs only at part of the pointsmentioned above. As a consequence, the possibility arises that theridges will give rise to a deviation in contact and fixation at thepoints mentioned above in relation to the ferrules inserted into thesleeve opposite each other and the terminals of the optical fibers beingconnected consequently will inevitably deviate from their mutual axialalignment.

SUMMARY OF THE INVENTION

[0009] It is, therefore, an object of the present invention to provide asleeve for optical connector ferrules which is capable of accuratelyabutting, aligning, and retaining opposed optical connector ferruleswhile incurring only sparingly such problems mentioned above as causinga deviation from axial alignment of the connected optical fibers andsuffering the sleeves to shed chips.

[0010] A further object of the present invention to provide a methodwhich, owing to the combination of a technique based on the conventionalmetal mold casting process or molding process with the quality of anamorphous alloy exhibiting a glass transition region, allows a sleevefor optical connector ferrules satisfying a predetermined shape,dimensional accuracy, and surface quality to be mass-produced with highefficiency by a simple process and, therefore, enables to omit ordiminish markedly such machining steps as grinding and consequentlyprovide an inexpensive sleeve for optical connector ferrules excellingin durability, strength, resistance to impact, and elasticity expectedof the sleeve.

[0011] To accomplish the object mentioned above, the first aspect of thepresent invention provides a sleeve for abutting, aligning, andretaining opposed optical connector ferrules, which sleeve ischaracterized by being manufactured from an amorphous alloy instead of aceramic material or metallic material which has been heretofore used.

[0012] The first embodiment of the sleeve for optical connector ferrulesaccording to the present invention is characterized by beingmanufactured from an amorphous alloy possessing at least a glasstransition region, preferably a glass transition region of a temperaturewidth of not less than 30 K. In a preferred embodiment, the sleeve ischaracterized by being formed of a substantially amorphous alloy havinga composition represented by the following general formula andcontaining an amorphous phase in a volumetric ratio of at least 50%:

X_(a)M_(b)Al_(c)

[0013] wherein X represents either or both of the two elements, Zr andHf, M represents at least one element selected from the group consistingof Mn, Fe, Co, Ni, and Cu, and a, b, and c represent such atomicpercentages as respectively satisfy 25≦a≦85, 5≦b≦70, and 0<c≦35.

[0014] The second embodiment of the sleeve according to the presentinvention, in view of the ease with which the optical connector ferrulesand the sleeve used for abutting, aligning, and retaining the terminalsof the ferrules succumb to deformation, is characterized by beingmanufactured from an amorphous alloy more susceptible of elasticdeformation than the material for the optical connector ferrules lestthe repetition of attachment and detachment of the sleeve and theferrules should inflict injury on the ferrules or compel the ferrules todevelop backlash.

[0015] The second aspect of the present invention, to give a sleeve ageometric shape fit for the purpose of abutting, aligning, and retainingopposed optical connector ferrules and to prevent the ferrules frombeing injured, consists in providing a sleeve characterized by having atubular body provided at three points on the inner wall surface thereofwith ridges extending from one to the other end of the tubular body inthe longitudinal direction thereof, the ridges being so formed that theupper faces thereof may have an arcuate cross section which curvestoward the axis of the tubular body.

[0016] The sleeve according to a preferred embodiment of the presentinvention is characterized by the fact that the tubular body mentionedabove is provided throughout the entire length in the longitudinaldirection thereof with such a slit as enables the optical connectorferrules to be elastically retained and preclude the occurrence ofbacklash even when the attachment and detachment of the sleeve and theferrules are repeated.

[0017] Another aspect of the present invention consists in providingmethods for the production of the sleeve for use with optical connectorferrules as mentioned above.

[0018] One mode of the methods is characterized by comprising the stepsof melting an alloying material capable of producing an amorphous alloyin a melting vessel having an upper open end, forcibly transferring theresultant molten alloy into a forced cooling casting mold disposed abovethe vessel and provided with at least one molding cavity, and rapidlysolidifying the molten alloy in the forced cooling casting mold toconfer amorphousness on the alloy thereby obtaining the product made ofan alloy containing an amorphous phase.

[0019] In a preferred embodiment of this method, the melting vessel isfurnished therein with a molten metal transferring member adapted toforcibly transfer the molten alloy upward, the forced cooling castingmold is provided with at least two identically shaped molding cavitiesand runners severally communicating with the cavities, and the runnersare disposed on an extended line of a transfer line for the molten metaltransferring member.

[0020] Another method is characterized by comprising the steps ofproviding a vessel for melting and retaining an alloying materialcapable of producing an amorphous alloy possessing a glass transitionregion, providing a metal mold provided with at least one cavity of theshape of the product aimed at, coupling a hole formed in, for example,the lower or upper part of the vessel with a sprue of the metal mold,for example by disposing the metal mold beneath or on the vessel,applying pressure on a melt of the alloy in the vessel thereby enablinga prescribed amount of the melt to pass through the hole of the vesseland fill the cavity of the metal mold, and solidifying the melt in themetal mold at a cooling rate of not less than 10 K(Kelvin scale)/sec.thereby giving rise to the product of an alloy containing an amorphousphase.

[0021] In any of the methods described above, as the alloying materialmentioned above, a material capable of producing a substantiallyamorphous alloy having a composition represented by the aforementionedgeneral formula: X_(a)M_(b)Al_(c), and containing an amorphous phase ina volumetric ratio of at least 50% is advantageously used.

[0022] Still another method of the present invention is characterized bycomprising the steps of heating an amorphous material formed of thealloy represented by the general formula mentioned above until thetemperature of a supercooled liquid region, inserting the resultant hotamorphous material into a container held at the same temperature,coupling with the container a metal mold provided with a cavity of theshape of the product aimed at, and forcing a prescribed amount of thealloy in the state of a supercooled liquid into the metal mold by virtueof the viscous flow thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Other objects, features, and advantages of the invention willbecome apparent from the following description taken together with thedrawings, in which:

[0024]FIG. 1 is a plan view illustrating one embodiment of the sleeve ofthe present invention;

[0025]FIG. 2 is a perspective view of the sleeve shown in FIG. 1;

[0026]FIG. 3 is a fragmentary cross-sectional view illustrating one modeof the use of the sleeve of the present invention;

[0027]FIG. 4 is a cross section taken through FIG. 3 along the lineIV-IV;

[0028]FIG. 5 is a fragmentary cross-sectional view illustrating anothermode of the use of the sleeve of the present invention;

[0029]FIG. 6 is a fragmentary cross-sectional view schematicallyillustrating one embodiment of the apparatus to be used for theproduction of the sleeve of the present invention;

[0030]FIG. 7 is a perspective view of a cast article manufactured by theapparatus shown in FIG. 6; and

[0031]FIG. 8 is a fragmentary cross-sectional view schematicallyillustrating another embodiment of the apparatus to be used for theproduction of the sleeve of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0032] According to one aspect of the present invention, the sleevewhich abuts, aligns, and retains the opposed optical connector ferrulesas described above is manufactured from an amorphous alloy. Theamorphous alloy manifests low hardness and high elasticity as comparedwith a ceramic material, exhibits high tensile strength and high bendingstrength, and excels in durability, impact resistance, surfacesmoothness, etc. and, therefore, constitutes itself the optimum materialfor the sleeve which abuts the opposed optical connector ferrules,aligns them without involving any deviation from axial alignment, andinfallibly retains them. The sleeve which has been manufactured from theamorphous alloy possessed of such characteristic properties as describedabove is such that the ridges of a semicircular cross section, forexample, to be formed on the inner wall surface thereof, therefore, donot easily injure the outer surfaces of the ferrules or do not easilydevelop backlash after the repetition of the attachment and detachmentof the ferrules to and from the sleeve but allow stable connectionbetween the opposed ferrules.

[0033] Further, the amorphous alloy possesses highly accuratecastability and machinability and, therefore, allows manufacture of asleeve of smooth surface faithfully reproducing the contour of thecavity of the mold by the metal mold casting method or molding method.The sleeve made of a ceramic material must be ground to a prescribedsize by all means after the step of sintering because this sleeve, onbeing sintered subsequently to primary formation, yields to contractionas described above. In sharp contrast, the sleeve made of an amorphousalloy permits omission of a step for adjustment of size or adjustment ofsurface coarseness or allows copious curtailment of such a step becausethis sleeve obviates the necessity for a sintering step and consequentlyprecludes the possibility of the produced sleeve from sustainingcontraction due to sintering. The sleeve which satisfies dimensionalprescription, dimensional accuracy, and surface quality, therefore, canbe manufactured by a single process with high mass producibility.

[0034] The material for the sleeve of the present invention does notneed to be limited to any particular substance but may be any of thematerials which are capable at all of furnishing a product formedsubstantially of amorphous alloy. Among other materials answering thisdescription, the Zr-TM-Al and Hf-TM-Al (TM: transition metal) amorphousalloys having very wide differences between the glass transitiontemperature (Tg) and the crystallization temperature (Tx) exhibit highstrength and high corrosion resistance, possess wide supercooled liquidranges (glass transition ranges), ΔTx=Tx−Tg, of not less than 30 K, andextremely wide supercooled liquid ranges of not less than 60 K in thecase of the Zr-TM-Al amorphous alloys. In the above temperature ranges,these amorphous alloys manifest very satisfactory workability owing toviscous flow even at such low stress not more than some tens MPa. Theyare characterized by being produced easily and very stably as evinced bythe fact that they are enabled to furnish an amorphous bulk materialeven by a casting method using a cooling rate of the order of some tensK/s. The aforementioned Zr-TM-Al and Hf-TM-Al amorphous alloys aredisclosed in U.S. Pat. No. 5,032,196 issued Jul. 16, 1991 to Masumoto etal., the teachings of which are hereby incorporated by reference. Aftera further study in search of uses for these alloys, the inventor hasascertained that by the metal mold casting from melt and by the moldingprocess utilizing the viscous flow resorting to the glass transitionrange as well, these alloys produce amorphous materials and permit veryfaithful reproduction of the shape and size of a molding cavity of ametal mold and, with the physical properties of the alloys as acontributory factor, befit the optical connector ferrules and the sleevefor connecting them.

[0035] The Zr-TM-Al and Hf-TM-Al amorphous alloys to be used in thepresent invention possess very large range of ΔTx, though variable withthe composition of alloy and the method of determination. TheZr₆₀Al₁₅Co₂ Ni₇ ₅Cu₁₅ alloy (Tg: 652 K, Tx: 768 K), for example, hassuch an extremely wide ΔTx as 116 K. It also offers very satisfactoryresistance to oxidation such that it is hardly oxidized even when it isheated in the air up to the high temperature of Tg. The Vickers hardness(Hv) of this alloy at temperatures from room temperature through theneighborhood of Tg is 460 (DPN), the tensile strength thereof is 1,600MPa, and the bending strength thereof is up to 3,000 MPa. The thermalexpansion coefficient, α of this alloy from room temperature through theneighborhood of Tg is as small as 1×10⁻⁶/K, the Young's modulus thereofis 91 GPa, and the elastic limit thereof in a compressed state exceeds4-5%. Further, the toughness of the alloy is high such that the Charpyimpact value falls in the range of 6-7 J/cm². This alloy, whileexhibiting such properties of very high strength as mentioned above, hasthe flow stress thereof lowered to the neighborhood of 10 MPa when it isheated up to the glass transition range thereof. This alloy, therefore,is characterized by being worked very easily and being manufactured withlow stress into minute parts and high-precision parts complicated inshape. Moreover, owing to the properties of the so-called glass(amorphous) substance, this alloy is characterized by allowingmanufacture of formed (deformed) articles with surfaces of extremelyhigh smoothness and having substantially no possibility of forming astep which would arise when a slip band appeared on the surface asduring the deformation of a crystalline alloy.

[0036] Generally, an amorphous alloy begins to crystallize when it isheated to the glass transition range thereof and retained therein for along time. In contrast, the aforementioned alloys which possess such awide ΔTx range as mentioned above enjoy a stable amorphous phase and,when kept at a temperature properly selected in the ΔTx range, avoidproducing any crystal for a duration up to about two hours. The user ofthese alloys, therefore, does not need to feel any anxiety about theoccurrence of crystallization during the standard molding process.

[0037] The aforementioned alloys manifest these properties unreservedlyduring the course of transformation thereof from the molten state to thesolid state. Generally, the manufacture of an amorphous alloy requiresrapid cooling. In contrast, the aforementioned alloys allow easyproduction of a bulk material of a single amorphous phase from a melt bythe cooling which is effected at a rate of about 10 K/s. The solid bulkmaterial consequently formed also has a very smooth surface. The alloyshave transferability such that even a scratch of the order of micronsinflicted by the polishing work on the surface of a metal mold isfaithfully reproduced.

[0038] When the aforementioned alloys are adopted as the alloyingmaterial for the sleeve, therefore, the metal mold to be used forproducing the formed article is only required to have the surfacethereof adjusted to fulfill the surface quality expected of the sleevebecause the molded product faithfully reproduces the surface quality ofthe metal mold. In the conventional metal mold casting method or moldingmethod, therefore, these alloys allow the steps for adjusting the sizeand the surface roughness of the molded article to be omitted ordiminished.

[0039] The characteristics of the aforementioned amorphous alloysincluding in combination relatively low hardness, high tensile strength,high bending strength, relatively low Young's modulus, high elasticlimit, high impact resistance, smoothness of surface, and highlyaccurate castability or workability render these alloys appropriate foruse as the material for the sleeve for the optical connector ferrules.They even allow these alloys to be molded for mass production by theconventional molding method.

[0040] The amorphous alloys represented by the general formula,X_(a)M_(b)Al_(c), mentioned above manifest the same characteristics asmentioned above even when they incorporate such elements as Ti, C, B,Ge, or Bi at a ratio of not more than 5 atomic %.

[0041] The advantages derived from adopting these alloys for the sleevewill be described more specifically below.

[0042] The first advantage resides in allowing mass-production of formedarticles of high accuracy. The inside diameter of the sleeve whichdirectly retains an optical connector ferrules or the diameter of acircle which passes the points of contact with the ferrule at the upperends of the ridges thereof is required to approximate as closely to theoutside diameter of the ferrule as possible. The formed articleheretofore obtained by injecting, degreasing, and sintering a ceramicmaterial fails to satisfy the dimensional accuracy and the surfacequality of a sleeve. It has been customary, therefore, to produce amolded article in a size allowing for machining and then finish it bycomplicated polishing treatments including abrasive finishing of theinside diameter by wire lapping using a diamond abrasive paste andabrasive finishing of the outside diameter. In the present invention,the use of a properly prepared metal mold in the casting and in theviscous flow forming (glass shaping) as well allows the formed articlesto be mass-produced without requiring a finish polishing or with asupplementary simple finish treatment. The method of the presentinvention is highly effective in producing sleeves satisfactory in termsof the roundness of the through-hole and the finish of the inner surfaceof the hole. The lengthy process of manufacture using a ceramicmaterial, therefore, can be curtailed in a great measure.

[0043] The second advantage consists in such mechanical properties ofthe sleeve as strength and toughness. Since the optical connectorferrules are frequently attached to and detached from the sleeverepeatedly, the sleeve must not settle, abrade, or crack. The hardness,strength, and toughness of the alloy mentioned above are enough topreclude the defects mentioned above.

[0044] According to the present invention, as described above, thesleeves satisfying the dimensional accuracy and the surface qualityrequired of the sleeves for optical connector ferrules can bemanufactured with high productivity at a low cost by the metal moldcasting method or molding method using the amorphous alloys having awide glass transition region such as the Zr-TM-Al and Hf-TM-Al amorphousalloys. Further, since the amorphous alloy to be used for the presentinvention excels in strength, toughness, and resistance to corrosion,the sleeves manufactured from this amorphous alloy withstand longservice without readily sustaining abrasion, deformation, chipping, orother similar defects.

[0045] The amorphous alloy possessed of the characteristics mentionedabove can be advantageously utilized for the ferrule and other componentparts of the optical connector and for the precision parts formicromachines as well as for the sleeve.

[0046] In still another embodiment of the present invention, the sleeveis manufactured from an amorphous alloy more susceptible of elasticdeformation than the material of the optical connector ferrules, namelyan amorphous alloy having Young's modulus lower than that of the ferruleby about 3-30 GPa, preferably 5-15 GPa. Owing to this specific choice ofmaterial, the sleeve allows opposed ferrules to be stably retainedeasily in a state aligning the axes thereof without the possibility ofsuffering the ferrules to sustain injury or develop backlash even whenthe ferrules are repeatedly attached to and detached from the sleeve.

[0047] As the material for ferrules to be used, ceramics and metals maybe used. Among other materials, an amorphous alloy, particularly theamorphous alloy having a composition represented by the aforementionedgeneral formula: X_(a)M_(b)Al_(c), and containing an amorphous phase ina volumetric ratio of at least 50% proves to be particularly desirablein terms of the mechanical properties, castability, and workabilitythereof as mentioned above. By the use of such an amorphous alloy,ferrules can be mass-produced by the metal mold casting method ormolding method (glass shaping) without requiring a finish polishing orwith a supplementary simple finish treatment. The use of the amorphousalloy is highly effective in producing ferrules satisfactory in terms ofthe roundness of the cross section of the minute fiber-insertion holeand the finish of the inner surface of the hole. The PC polishing whichis usually performed on the leading end of a ferrule to impart thespherical convex surface thereto for the purpose of ensuring intimatecontact of glass fibers is no longer necessary. It suffices to performthe final polish after the optical fiber has been set in position. Thelengthy process of manufacture using a metallic material and a ceramicmaterial, therefore, can be curtailed in a great measure. The sameremarks hold good for the outside diameter of the ferrule and thecoincidence between the axis of the outside diameter and the axis of theminute fiber-insertion hole of the ferrule.

[0048] In the second aspect of the present invention, the sleeve isvested with such a geometric shape as fits the purpose of retaining theopposed ferrules as aligned mutually to the axes thereof withoutinflicting injury on the ferrules.

[0049] Now, the shape of the sleeve of the present invention will bedescribed below with reference to the drawings annexed hereto.

[0050]FIG. 1 and FIG. 2 illustrate one preferred mode of embodying thesleeve of the present invention; FIG. 1 is a plan view of the sleeve andFIG. 2 a perspective view thereof.

[0051] This sleeve 1 comprises a tubular body 2, ridges (elongateelevations) 3 raised from the inner wall surface of the tubular body 2at three points as extended from one to the other end thereof in thelongitudinal direction, and a slit 4 formed in the wall of the tubularbody 2 throughout the entire length in the longitudinal directionthereof.

[0052] The ridges 3, for the purpose of avoiding infliction of injury onthe ferrules, are required to have an arcuate upper face convex towardthe axis of the tubular body 2 and a cross section such as, for example,a substantially semicircular cross section, a substantially semiellipticcross section, a triangular cross section containing a rounded upperend, etc. Preferably, the ridges 3 assume such a substantiallysemicircular cross section as is illustrated in FIG. 1. By having theridges 3 of this description provided on the inner wall surface of thetubular body 2 at three points as extended in the longitudinaldirection, the sleeve 1 is enabled to retain the ferrules therein in astate nipped at three points of the ridges contacting the outer wallsurfaces of the ferrules. As a result, the sleeve 1 is capable of stablyretaining the abutted ferrules as mutually aligned to the axes of theferrules (and consequently of the optical fibers being connected)without inflicting injury on the ferrules. When the ridges have an acuteupper end for the sake of the point contact mentioned above, they are ata disadvantage in suffering the upper ends to concentrate the loadexerted thereon and tend to inflict injury on the outer surfaces of theferrules. When the ridges are provided at four or more points on theinner wall surface of the sleeve, they tend to cause deviation in thepoints of contact and fixation of the opposed ferrules inserted in thesleeve and tend to disrupt the coincidence of the axes of the opticalfibers being connected.

[0053] The ridges are preferred to be disposed as equally spaced atthree points on the inner wall surface of the tubular body 2, though aslight deviation in the regular spacing is tolerable. Though the heightof the ridges 3 has only to satisfy the requirement that the ridges 3 becapable of stably retaining the ferrules, it is generally preferred tobe in the range of about 0.1-1.0 mm (about 0.1-1.0 mm in radius in thecase of the ridges having a semicircular cross section). While theridges 3 are preferred to be a continued elevation, they maydiscontinuously extend throughout the entire length of the tubular bodyas occasion demands.

[0054] The sleeve 1, as described above, has the slit 4 formed in thewall thereof throughout the entire length in the longitudinal direction.Even with a precision sleeve which is not furnished with this slit, thepresent invention attains the aforementioned effect due to the use ofsuch an amorphous alloy as the material as mentioned above and theeffect due to the formation of the ridges mentioned above. The provisionof the slit 4, however, is advantageous in enhancing the elasticity ofthe sleeve 1, enabling the sleeve to nip stably the opposed ferruleselastically as aligned mutually to their axes even in the presence ofmore or less dispersion of dimensional accuracy, and permitting theferrules to be repeatedly attached to and detached from the sleevewithout rendering the development of backlash in the state of retentionof ferrules.

[0055] As respects the mechanical properties of the material itself forthe sleeve 1, the sleeve 1 is preferred to manifest a Young's modulus inthe approximate range of 90-99 GPa and an elastic limit in theapproximate range of 1% to several %. The sleeve of the presentinvention is manufactured from an amorphous alloy, a material sharplycontrasted to the ceramic material of the conventional sleeve such as,for example, zirconia which is nearly devoid of elasticity. This sleeve,therefore, excels in elastic properties such that it fully tolerates therepeated attachment and detachment of ferrules.

[0056]FIG. 3 and FIG. 4 illustrate one mode of the use of the sleeve 1of the present invention in optical connectors. The sleeve 1 presumesuse of ferrules 10 each of a one-piece construction comprising acapillary part 11 and a flange part 12.

[0057] Specifically, this ferrule 10 is composed of the capillary part11 which has formed along the axis thereof a through-hole 13 of a smalldiameter intended for the insertion of an optical fiber 17 (or the basicthread of an optical fiber coated with a plastic thin film) and theflange part 12 which has formed along the axis thereof a through-hole 14of a large diameter intended for the insertion of a sheathed opticalfiber 16 (the optical fiber coated with a sheath 18). The through-hole13 of the small diameter and the through-hole 14 of the large diameterare connected into each other through a tapered part 15.

[0058] The attachment of the optical fiber to the ferrule 10 of thisconstruction is fulfilled by stripping the leading end part of thesheathed optical fiber 16 of the sheath 18 to expose the optical fiber17 in a prescribed length, applying an adhesive agent to the exposedoptical fiber and the leading end part of the sheathed optical fiber,inserting the exposed optical fiber 17 into the through-hole 13 of thesmall diameter in the ferrule 10 from the flange part side thereof, andallowing the leading end parts of the optical fiber 17 and the sheathedoptical fiber 16 to be immobilized with the adhesive agent in thethrough-holes 13 and 14 of the ferrule 10.

[0059] The connection of a pair of optical fibers 17, 17 is attained byinserting into the sleeve 1 through the opposite ends thereof theferrules 10, 10 having the optical fibers already inserted and joinedtherein and then abutting the end parts of the ferrules 10, 10. As aresult, the optical fibers 17, 17 are allowed to have their leading endparts abutted and joined in a state having the axes thereof aligned toeach other.

[0060] The circle 5 (FIG. 1) which passes the upper ends of the ridges 3at the three points of the sleeve 1 has a diameter slightly smaller thanthe outside diameter of the capillary part 11 of the ferrule 10. Whenthe ferrules 10, 10 are inserted into the sleeve 1 through the oppositeends thereof, therefore, the sleeve 1 is slightly pushed open andultimately enabled to retain the capillary parts 11, 11 in anelastically nipped state.

[0061]FIG. 5 illustrates another mode of using the sleeve 1 of thepresent invention in optical connectors. A ferrule 10 a uses a capillarypart 11 a and a flange part 12 a as separate components.

[0062] Specifically, this ferrule 10 a is composed of the capillary 11 awhich has formed along the axis thereof a through-hole 13 a of a smalldiameter intended for the insertion of the optical fiber 17 and theflange 12 a which has formed along the axis thereof a through-hole 14 aof a large diameter for the insertion of the sheathed optical fiber 16.It is assembled by fixing the end part of the capillary lla enclosing atapered hole 15 a therein in an leading end hole part 19 of the flange12 a by virtue of tight fit or adhesion. The through-hole 13 a of thesmall diameter in the capillary lla and the through-hole 14 a of thelarge diameter in the flange 12 a are joined through the medium of atapered hole part 15 a.

[0063] The method for joining the optical fiber to the ferrule 10 a andthe mode of attachment of the sleeve 1 and the ferrules 10 a, 10 a arethe same as those of the embodiment illustrated in FIG. 3 and FIG. 4.

[0064]FIG. 6 schematically illustrates one mode of embodying anapparatus and method for the production of the sleeve of the presentinvention by the metal mold casting technique.

[0065] A forced cooling casting mold 20 is a split mold composed of anupper mold 21 and a lower mold 26. The upper mold 21 has a pair ofmolding cavities 22 a, 22 b formed therein and adapted to define theoutside dimension of a sleeve. Inside these cavities 22 a, 22 b, cores25 a, 25 b for defining the inside dimension of the sleeve are formedrespectively. These cavities 22 a, 22 b intercommunicate through themedium of a runner 23 such that the molten metal flows through theleading ends of such parts 24 a, 24 b of the runner as half encircle theperipheries of the cavities 22 a, 22 b at a prescribed distance into thecavities 22 a, 22 b. On the other hand, a sprue (through-hole) 27communicating with the runner 23 mentioned above is formed at apertinent position of the lower mold 26. Underneath the sprue 27 isformed a depression 28 which is shaped to conform with a cylindrical rawmaterial accommodating part or pot 32 constituting itself an upper partof a melting vessel 30.

[0066] The cores 25 a, 25 b, when necessary, may be formed integrallywith the lower mold 26. While the forced cooling casting mold 20 can bemade of such metallic material as copper, copper alloy, cemented carbideor superalloy, it is preferred to be made of such material as copper orcopper alloy which has a large thermal capacity and high thermalconductivity for the purpose of heightening the cooling rate of themolten alloy poured into the cavities 22 a, 22 b. The upper mold 21 mayhave disposed therein such a flow channel as allow flow of a coolingmedium like cooling water or cooling gas.

[0067] The melting vessel 30 is provided in the upper part of a mainbody 31 thereof with the cylindrical raw material accommodating part 32and is disposed directly below the sprue 27 of the lower mold 26 in sucha manner as to be reciprocated vertically. In a raw materialaccommodating hole 33 of the raw material accommodating part 32, amolten metal transferring member or piston 34 having nearly the samediameter as the raw material accommodating hole 33 is slidably disposed.The molten metal transferring member 34 is vertically moved by a plunger35 of a hydraulic cylinder (or pneumatic cylinder) not shown in thediagram. An induction coil 36 as a heat source is disposed so as toencircle the raw material accommodating part 32 of the melting vessel30. As the heat source, any arbitrary means such as one resorting to thephenomenon of resistance heating may be adopted besides thehigh-frequency induction heating. The material of the raw materialaccommodating part 32 and that of the molten metal transferring member34 are preferred to be such heat-resistant material as ceramics ormetallic materials coated with a heat-resistant film.

[0068] Incidentally, for the purpose of preventing the molten alloy fromforming an oxide film, it is preferred to dispose the apparatus in itsentirety in a vacuum or an atmosphere of an inert gas such as Ar gas orestablish a stream of an inert gas at least between the lower mold 26and the upper part of the raw material accommodating part 32 of themelting vessel 30.

[0069] The production of the sleeve of the present invention is effectedby first setting the melting vessel 30 in a state separated downwardlyfrom the forced cooling casting mold 20 and then charging the emptyspace overlying the molten metal transferring member 34 inside the rawmaterial accommodating part 32 with the alloying raw material A of acomposition capable of yielding such an amorphous alloy as mentionedabove. The alloying raw material A to be used may be in any of thepopular forms such as rods, pellets, and minute particles.

[0070] Subsequently, the induction coil 36 is excited to heat thealloying raw material A rapidly. After the fusion of the alloying rawmaterial A has been confirmed by detecting the temperature of the moltenmetal, the induction coil 36 is demagnetized and the melting vessel 30is elevated until the upper end thereof is inserted in the depression 28of the lower mold 26. Then, the hydraulic cylinder is actuated to effectrapid elevation of the molten metal transferring member 34 through themedium of the plunger 35 and injection of the molten metal through thesprue 27 of the casting mold 20. The injected molten metal is advancedthrough the runner 23, 24 a, 24 b, introduced into the cavities 22 a, 22b and compressed and rapidly solidified therein. In this case, thecooling rate exceeding 10³ K/s can be obtained by suitably setting suchfactors as injection temperature and injection speed, for example.Thereafter, the melting vessel 30 is lowered and the upper mold 21 andthe lower mold 26 are separated to allow extraction of the product.

[0071] The shape of the cast product manufactured by the methoddescribed above is illustrated in FIG. 7. The sleeves 1 possessed of asmooth surface faithfully reproducing the cavity surface of the castingmold as illustrated in FIG. 1 and FIG. 2 are obtained by severing runnerparts 42 a, 42 b from sleeve parts 41 a, 41 b of a cast product 40 andgrinding the cut faces of the sleeve parts remaining after by theseverance.

[0072] The high-pressure die casting method described above allows acasting pressure up to about 100 MPa and an injection speed up to aboutseveral m/s and enjoys the following advantages.

[0073] (1) The charging of the mold with the molten metal completeswithin several milliseconds and this quick charging adds greatly to theaction of rapid cooling.

[0074] (2) The highly close contact of the molten metal to the mold addsto the speed of cooling and allows precision molding of molten metal aswell.

[0075] (3) Such faults as shrinkage cavities possibly occurring duringthe shrinkage of a cast article due to solidification can be allayed.

[0076] (4) The method allows manufacture of a formed article in acomplicated shape.

[0077] (5) The method permits smooth casting of a highly viscous moltenmetal.

[0078]FIG. 8 illustrates schematically the construction of another modeof embodying the apparatus and method for producing the sleeve of thepresent invention.

[0079] In FIG. 8, the reference numeral 60 denotes a vessel for meltingan alloying material capable of producing such an amorphous alloy asmentioned above and holding the produced melt therein. Beneath thisvessel 60 is disposed a split metal mold 50 having cavities 52 a, 52 bof the shape of a product aimed at. Any of such known heating means (notshown) as, for example, the high-frequency induction heating and theresistance heating may be adopted for heating the vessel 60.

[0080] The construction of the metal mold 50 is substantially identicalwith the mold 20 illustrated in FIG. 6 mentioned above except that thevertical positional relation is reversed. Specifically, an upper mold 56has formed in the upper part of a sprue (through-hole) 57 a depression58 for accommodating the lower end part of the vessel 60 and correspondsto the lower mold 26 shown in FIG. 6. Meanwhile, a lower mold 51 isidentical with the upper mold 21 shown in FIG. 6 except that moldingcavities 52 a, 52 b, runners 53, 54 a, 54 b, and cores 55 a, 55 b havetheir shapes and modes of disposition reversed from those of FIG. 6.This metal mold 50, when necessary, may have the cores 55 a, 55 b formedintegrally with the upper mold 56.

[0081] The production of sleeves are carried out by connecting a smallhole 61 formed in the bottom part of the vessel 60 to the sprue 57 ofthe metal mold 50, applying pressure to the molten alloy A′ in thevessel 60 through the medium of inert gas thereby forwarding the moltenalloy A′ from the small hole 61 in the bottom of the vessel 60 throughthe runners 53, 54 a, and 54 b into the cavities 52 a, 52 b until thesecavities are filled with the molten alloy A′ to capacity, andsolidifying the molten alloy at a cooling rate preferably exceeding 10K/s to obtain the sleeve made of an alloy consisting substantially of anamorphous phase.

[0082] By the procedure just described, the sleeve can be produced whichmanifests a dimensional accuracy, L, in the range of ±0.0005 to ±0.001mm and a surface accuracy in the range of 0.2 to 0.4 μm.

[0083] The method, as described above, manufactures two cast products bya single process using a metal mold provided with a pair of moldingcavities. Naturally, the present invention can manufacture three or morecast products by using a metal mold provided with three or more cavitiestherein.

[0084] Besides the alloy casting method described above, the extrusionmolding is also available for the manufacture of the sleeve. Since theamorphous alloy mentioned above possesses a large supercooled liquidregion ΔTx, the sleeve can be obtained in a prescribed shape by heatinga material of this amorphous alloy to a temperature in the supercooledliquid region, inserting the hot material in a container retained at thesame temperature, connecting this container to the metal mold providedwith the cavity of the shape of a sleeve product aimed at, pressing aprescribed amount of the heated alloy into the cavity by virtue of theviscous flow of the supercooled liquid, and molding the alloy.

[0085] Now, the present invention will be described more concretelybelow with reference to working examples which have demonstrated theeffect of the present invention specifically.

[0086] Example 1:

[0087] By using the apparatus shown in FIG. 6 and employing theproduction conditions of an injection temperature of 1273 K, injectionspeed of 1 m/s, casting pressure of 1 MPa, and loading time of 100milliseconds, a sleeve of an amorphous alloy having a composition ofZr₆₅Al₁₀Ni₁₀Cu₁₅ and the shape shown in FIG. 1 and FIG. 2 with an insidediameter of 2.5 mm, an outside diameter of 3.1 mm, and a curvatureradius of ridges of 0.3 mm was manufactured.

[0088] The sleeve obtained was a product having an outstanding surfacesmoothness faithfully reproducing the contour of the cavity of the metalmold. It was found to manifest a Young's modulus of 80 GPa, bendingstrength of 2,970 MPa, Vicker's hardness of 400 (DPN), and a thermalexpansion coefficient, α, of 0.95×10⁻⁵/K.

[0089] By the same method, a ferrule of an amorphous alloy having acapillary part and a flange part formed integrally as shown in FIG. 3was manufactured. This ferrule was found to have a composition ofZr₆₀Al₁₅Co₂ ₆Ni₇ ₅Cu₁₅ and manifest a Young's modulus of 91 GPa. Wheneach end of two optical fibers was joined to two such ferrulesmanufactured as described above and the two ferrules were fit into thesleeve mentioned above through the opposite ends thereof, the opticalfibers could be stably connected without causing any deviation from theaxial alignment of the optical fibers.

[0090] Example 2:

[0091] Various alloys including Zr₆₀Al₁₅Co₂ ₅Ni₇ ₅Cu₁₅ and shown in thefollowing table were manufactured by melting relevant component metals.They were each placed in a quartz crucible and melted thoroughly byhigh-frequency induction heating. The melt was injected under a gaseouspressure of 2 kgf/cm² through a slender hole formed in the lower part ofthe crucible into a copper casting mold provided with a cylindricalcavity, 2 mm in diameter and 30 mm in length, and kept at roomtemperature to obtain a rod-like specimen for the determination ofmechanical properties. The results of this determination are shown inthe TABLE α 10⁻⁵/K Tensile Bending (room Hard- strength strengthtempera- E ness Tg Tx Alloy used (MPa) (MPa) ture-Tg) (GPa) Hv (K) (K)Zr₆ ₇Cu₃ ₃ 1,880 3,520 0.8 99 540 603 669 Zr₆ ₅Al₇ ₅Cu₂ ₇  ₅ 1,450 2,7100.8 93 420 622 732 Zr₆ ₅Al₇ ₅Ni₁ ₀Cu₁ ₇  ₅ 1,480 2,770 0.9 92 430 630736 Zr₆ ₀Al₁ ₅Co₂ ₅Ni₇ ₅Cu₁ ₅ 1,590 2,970 1.0 91 460 652 768

[0092] It is clearly noted from the table that the produced amorphousalloy materials showed such magnitudes of bending strength as notablysurpass the magnitude (about 1,000 MPa) of the partially stabilizedzirconia heretofore adopted as the material for the sleeve, suchmagnitudes of Young's modulus as approximate one half, and suchmagnitudes of hardness as approximate one third thereof, indicating thatthese alloy materials were vested with properties necessary as thematerial for the sleeve.

[0093] Example 3:

[0094] A metal mold of steel as illustrated in FIG. 6 and a metallicextruder were connected and a sleeve was manufactured by extruding thesame alloy as used in Example 1. For the extrusion, amorphous billets,25 mm in diameter and 40 mm in length, of the same alloy preparedseparately by casting were used. The billets were preheated to 730 K andthe container of the extruder and the inlet part and the molding part ofthe metal mold were similarly preheated to 730 K. The hot billets wereinserted into the container of the extruder and then injected into themetal mold. The metal mold was cooled. Then the formed article wasremoved from the mold, deprived of the inlet part, and inspected. Theoutward appearance, the dimensional accuracy, the surface roughness,etc. of the formed article were found to be nearly equal to those of thesleeve obtained in Example 1.

[0095] While certain specific embodiments and working examples have beendisclosed herein, the invention may be embodied in other specific formswithout departing from the spirit or essential characteristics thereof.The described embodiments and examples are therefore to be considered inall respects as illustrative and not restrictive, the scope of theinvention being indicated by the appended claims rather than by theforegoing description and all changes which come within the meaning andrange of equivalency of the claims are, therefore, intended to beembraced therein.

What is claimed is:
 1. A sleeve for abutting, aligning, and retainingopposed optical connector ferrules, which sleeve is made of an amorphousalloy possessing at least a glass transition region.
 2. The sleeveaccording to claim 1 , wherein said glass transition region has atemperature width of not less than 30 K.
 3. The sleeve according toclaim 1 , wherein said glass transition region has a temperature widthof not less than 60 K.
 4. A sleeve for abutting, aligning, and retainingopposed optical connector ferrules, which sleeve is made of asubstantially amorphous alloy having a composition represented by thefollowing general formula and containing an amorphous phase in avolumetric ratio of at least 50%: X_(a)M_(b)Al_(c) wherein X representsat least one element selected from the group consisting of Zr and Hf, Mrepresents at least one element selected from the group consisting ofMn, Fe, Co, Ni, and Cu, and a, b, and c represent such atomicpercentages as respectively satisfy 25≦a≦85, 5≦b≦70, and 0<c≦35.
 5. Asleeve for abutting, aligning, and retaining opposed optical connectorferrules, which sleeve is made of an amorphous alloy more susceptible ofelastic deformation than the material for the optical connectorferrules.
 6. A sleeve for abutting, aligning, and retaining opposedoptical connector ferrules, comprising a tubular body and three ridgesprovided on an inner wall surface of the tubular body, each of saidridges extending from one to the other end of the longitudinal directionof said tubular body and having an upper face assuming an arcuate crosssection which curves toward an axis of said tubular body.
 7. The sleeveaccording to claim 6 , wherein said tubular body has a slit formedthroughout the entire length in the longitudinal direction thereof. 8.The sleeve according to claim 6 , wherein each of said ridges has asubstantially semicircular cross section.
 9. The sleeve according toclaim 6 , wherein each of said ridges has a substantially semiellipticcross section.
 10. The sleeve according to claim 6 , wherein each ofsaid ridges has a triangular cross section containing a rounded upperend.
 11. The sleeve according to claim 6 , wherein each of said ridgescontinuously or discontinuously extends the entire length of saidtubular body.
 12. The sleeve according to claim 6 , wherein each of saidridges has a height of 0.1 to 1.0 mm.
 13. The sleeve according to claim6 , wherein said sleeve is made of an amorphous alloy possessing a glasstransition region of a temperature width of not less than 30 K.
 14. Thesleeve according to claim 6 , wherein said sleeve is made of asubstantially amorphous alloy having a composition represented by thefollowing general formula and containing an amorphous phase in avolumetric ratio of at least 50%: X_(a)M_(b)Al_(c) wherein X representsat least one element selected from the group consisting of Zr and Hf, Mrepresents at least one element selected from the group consisting ofMn, Fe, Co, Ni, and Cu, and a, b, and c represent such atomicpercentages as respectively satisfy 25≦a≦85, 5≦b≦70, and 0<c ≦35.
 15. Amethod for the production of a sleeve for optical connector ferrules,comprising the steps of: providing a melting vessel having an upper openend; providing a forced cooling casting mold provided with at least onemolding cavity and disposed above said melting vessel; melting analloying material capable of yielding an amorphous alloy in said meltingvessel; forcibly transferring the resultant molten alloy into themolding cavity of said forced cooling casting mold; and rapidlysolidifying said molten alloy in said forced cooling casting mold toconfer amorphousness on the alloy thereby obtaining a cast product of analloy containing an amorphous phase.
 16. The method according to claim15 , wherein said melting vessel has a molten metal transferring memberdisposed in the vessel and adapted to forcibly transfer the molten alloyupward, and said forced cooling casting mold is provided with at leasttwo identically shaped molding cavities and runners communicating withsaid cavities, said runners being disposed on an extended line of atransfer line for the molten metal transferring member.
 17. The methodaccording to claim 16 , wherein said molten metal transferring member iscaused to transfer forcibly the molten alloy in said melting vessel intothe molding cavities of said forced cooling casting mold and meanwhileexert pressure on said molten alloy filling the molding cavities of saidforced cooling casting mold.
 18. The method according to claim 15 ,wherein said forced cooling casting mold is a water-cooled casting moldor gas-cooled casting mold.
 19. The method according to claim 15 ,wherein said alloying material has a composition represented by thefollowing general formula and is endowed with an ability to yield asubstantially amorphous alloy containing an amorphous phase in avolumetric ratio of at least 50%: X_(a)M_(b)Al_(c) wherein X representsat least one element selected from the group consisting of Zr and Hf, Mrepresents at least one element selected from the group consisting ofMn, Fe, Co, Ni, and Cu, and a, b, and c represent such atomicpercentages as respectively satisfy 25≦a≦85, 5≦b≦70, and 0<c≦35.
 20. Themethod according to claim 15 , wherein said melting of said alloyingmaterial in said melting vessel is carried out in a vacuum or under anatmosphere of inert gas.
 21. A method for the production of a sleeve foroptical connector ferrules, comprising the steps of: providing a vesselfor melting an alloying material capable of producing an amorphous alloypossessing a glass transition region, said vessel being provided with ahole and retaining a melt of said alloying material; providing a metalmold provided with a sprue and at least one cavity of the shape of aproduct aimed at; connecting said hole formed in said vessel to thesprue of said metal mold; applying pressure on said melt in the vesselto introduce a prescribed amount of said melt via the hole of saidvessel into said metal mold thereby filling said cavity with said melt;and solidifying said melt in said metal mold at a cooling rate of notless than 10 K/s to obtain a product of an alloy containing an amorphousphase.
 22. The method according to claim 21 , wherein said alloyingmaterial has a composition represented by the following general formulaand endowed with an ability to yield a substantially amorphous alloycontaining an amorphous phase in a volumetric ratio of at least 50%:X_(a)M_(b)Al_(c) wherein X represents at least one element selected fromthe group consisting of Zr and Hf, M represents at least one elementselected from the group consisting of Mn, Fe, Co, Ni, and Cu, and a, b,and c represent such atomic percentages as respectively satisfy 25≦a≦85,5≦b≦70, and 0<c≦35.
 23. A method for the production of a sleeve foroptical connector ferrules, comprising the steps of: heating anamorphous material formed of an alloy represented by the followinggeneral formula and containing an amorphous phase in a volumetric ratioof at least 50% to a temperature in a supercooled liquid region:X_(a)M_(b)Al_(c) wherein X represents at least one element selected fromthe group consisting of Zr and Hf, M represents at least one elementselected from the group consisting of Mn, Fe, Co, Ni, and Cu, and a, b,and c represent such atomic percentages as respectively satisfy 25≦a≦85,5≦b≦70, and 0<c≦35; inserting the resultant hot amorphous material in acontainer held at the same temperature; connecting a metal mold providedwith a cavity of the shape of a product aimed at to said container; andintroducing a prescribed amount of said alloy under pressure into saidmetal mold by virtue of the viscous flow of said supercooled liquid toform a sleeve.